After every major aircraft accident, media reports are rife with speculation about the cause. This is especially so in the case of high profile accidents that generate international interest, such as the loss of Air France Flight 447, the Airbus A330-200 that was lost over the Atlantic several days ago. In this particular case, the situation is complicated by the fact that very little factual information about what happened is available.In the past few days, much speculation by the press has centered on reports of ACARS messages transmitted by the aircraft while it was en route, which may have indicated 'speed sensor' problems. Presumably, the 'speed sensors' in question are the aircraft's pitot tubes and the electronics associated with processing data they provide.
I thought it would be useful to set forth the contents of official statements on the issue made by the Bureau d'Enquêtes et d'Analyses (BEA) -- the French accident investigation agency -- and Air France. Together, these statements amount to the only factual information that is available at this time.
A statement released yesterday by the BEA about AF447 confirmed that the accident aircraft transmitted automated messages that indicated inconsistency between different speed measures. No more, no less. Here is the link to the BEA press release (in French).
Today, Air France addressed the issue with a press release of its own. The Air France press release about the pitot tubes is presented here in its entirety:
Following the many questions which have appeared in the media on the issue of the Pitot probes in its fleet (the Pitot probe is an instrument which measures the air speed of the aircraft), Air France wishes to make the following clarifications:Source: Flight Air France 447 Rio de Janeiro - Paris-Charles de Gaulle, Press Release No. 12
1) Malfunctions in the Pitot probes on the A 320 led the manufacturer to issue a recommendation in September 2007 to change the probes. This recommendation also applies to long-haul aircraft using the same probes and on which a very few incidents of a similar nature had occurred.
It should be noted that a recommendation from the manufacturer gives the operator total freedom to apply the corresponding guidelines fully, partially or not at all. Should flight safety be concerned, the manufacturer, together with the authorities, issues a mandatory service bulletin followed by an airworthiness directive (AD).
The recommendation to change the probes was implemented by Air France on its A320 fleet where this type of incident involving water ingress had been observed. It was not implemented on the A340/330s as no such incidents had been noted.
2) Starting in May 2008 Air France experienced incidents involving a loss of airspeed data in flight, in cruise phase on A340s and A330s. These incidents were analysed with Airbus as resulting from pitot probe icing for a few minutes, after which the phenomenon disappeared. Discussions subsequently took place with the manufacturer. Air France asked for a solution which would reduce or eliminate the occurrence of these incidents. In response to these requests, the manufacturer indicated that the probe model recommended for the A320 was not designed to prevent such incidents which took place at cruise levels, and reiterated the operational procedures well-known to the crews.
In the first quarter of 2009 laboratory tests suggested, however, that the new probe could represent a valuable improvement to reduce the incidence of high altitude airspeed discrepancy resulting from pitot probe icing, and an in service evaluation in real flight conditions was proposed by Airbus. Without waiting for the in service evaluation, Air France decided to replace all its probes and the programme was launched on 27 April 2009.
Without making any assumptions as to a possible link with the causes of the accident, Air France speeded up this programme and reminded its pilots of the current instructions issued by the manufacturer to cope with the loss of airspeed data.
RELATED: Click here to view all posts about Air France Flt 447 on Aircrew Buzz.
